Problem: $ {4\cdot \left[ \begin{array}{cc} -1 & 3 \\ 4 & 1 \end{array} \right]=}$
Answer: The Strategy To multiply a matrix by a scalar, we multiply each term of the matrix by the scalar. Multiplying each term $ {\begin{aligned}4\cdot \left[\begin{array}{rr} {-1} & {3} \\ {4} & {1} \end{array}\right]&=\left[\begin{array}{rr} 4\cdot{-1} & 4\cdot{3} \\ 4\cdot{4} & 4\cdot{1} \end{array}\right] \\\\&=\left[\begin{array}{rr} {-4} & {12} \\ {16} & {4} \end{array}\right]\end{aligned}}$ Summary $ {4\cdot \left[ \begin{array}{cc} -1 & 3 \\ 4 & 1 \end{array} \right]=\left[ \begin{array}{cc} -4 & 12 \\ 16 & 4 \end{array} \right]}$